Intro: Intakes intakes intakes... there are so many to choose from. Some of the more popular ones are CWC and M2's cold air boxes. These draw air from a duct the runs straight down from the box and draws air from next to the radiator. Without question a great design but at a price and sometimes fitment is questionable. The advantages are clear however. Cold air that doesn't rob the intercooler of air because unlike the stock design it doesn't connect to the intercooler's duct. Another advantage to these boxes is the size because it allows for larger intercoolers. The other popular design is basically just cone filters stuck to the end of the two intake hoses. Nothing like sucking hot air from the engine bay right after it passes through the radiator. But hey, you can always come up with some inexpensive heat shielding however even the best shielding will allow hot air to be sucked in. And there are others like the PFS box (outdated) and the Pettit intake (umm yea). For a long time I used a basic Racing Beat intake duct along with the stock box and a K&N filter. A very adequate design but it robed the intercooler or air, was bulky, used the crappy accordion rubber hoses and blocked the radiators air flow. A good intake was therefore on my list but nothing ever really cried out to me so I decided the bolt-on designs just weren't for me. The solution? Build my own from scratch and we aren't talking drilling some holes in the bottom of the stock box or coming up with some Home Depot special. This intake is serious business!

Design Concept: There are several unique design elements incorporated in to my design. To start with it is a cold air system but does NOT use a box like other cold air systems. (Many other cars don't use boxes for cold air systems but since the Rx-7 essentially has two intake tracks a box is almost always used.) Both the primary and secondary turbo intake tracks have separate, fully enclosed, intakes. The primary turbo's (towards the front) intake draws air from beside the radiator much like the M2 style boxes. However these boxes draw air from the main opening in the nose, which feeds the radiator. Since the duct terminates next to the radiator it is possible for air to be sucked from the engine bay, down through the radiator and up in to the intake at idle. My car has a custom under tray that separates the intake from the main opening. It sucks air from under the car. The second turbo's (further back) intake shares the opening with the intercooler just like the stock box does. However due to the fact that this is the second turbo there is no chance of air being sucked from the engine bar, through the intercooler and in to the intake at idle because the turbo only operates at speed. Air is only robbed from the intercooler when the second turbo is activated at around 4500 RPM. The air pump is also plumbed in to this intake section. The air pump operates at below about 3000 RPM so it doesn't effect the intake while operating. It was important to deliver cold air to the air pump because hot air can damage the pump, or so I have heard. Both intakes use mandrel bent stainless pipe, which offers an advantage over the accordion hoses that create turbulent air. Lastly, since there is no box the radiator has an unobstructed path for air flow.

Materials: Adding up the money spent on buying the required materials along with the time spent finding them and designing/building the intake basically brings me to the conclusion that I didn't save any money with this project. Saving money really wasn't what this was about though. Below is a list of the materials I bought along with price and source.

* This Kool Blue filter was sent to me free of charge from Accell customer service. I had trouble with a stock replacement filter I bought for my Mx-3 and was dealing with them directly. The filter took a long time to get and was not a correct fit. Kool Blue corrected this problem by creating a new filter design for the Mx-3 and sending me the very first one. When I asked about the cone filter they also sent that to me for free. Their customer service impressed me beyond any other company I have ever dealt with. This filter is worth about $50.00 and the quality is very impressive.

Construction: Not including design time this intake probably took around 30 hours to fabricate, maybe more. From conception to completion this took over two years. What follows is a detailed explanation of the construction process with a few more notes about design.

1. Primary turbo's filter: This involved one bend up and another forward. Due to limitations with mandrel bending of pipe the first bend is not tight enough so I had to put the silicone hose on at a slight angle, which wasn't a problem because at 2.5" in diameter it is slightly larger (and thus lose) than the turbo inlet. Since I knew I would be cutting it close with how much mandrel bent material I had with one J bend I got a filter with a 20 deg outlet. This not only saved me a little material but also offered a slight adjustment margin because I can rotate the filter on the pipe and get different fitment.
2. Secondary turbo's filter: As you can see by the picture this pipe is much longer and has a good many bends. First it had to take a slight bend down and to the right to clear the strut bar. Next it takes a long straight path to a S bend to arrive at the filter. Tolerances are tight and there is minor rubbing against the air pump's pulley under hard right hand cornering. I with correct this by heating up the pipe and pushing it in about 1/4 of an inch at the rubbing location. The pipe is held in place by not only the turbo and ducting but also a bracket attached to the chassis. This bracket might be the cause of my issues with rubbing but I feel it is a good addition. Both pipes will be receiving a coat of high temperature ceramic clear coat paint. The stainless pipe is rusting a bit so the paint will not only protect the finish but also block a bit of heat. After my friend helped me weld the segments of pipe together I was left with less than 2" of leftover pipe.
3. Air Pump: This was perhaps the most tricky part. After welding the bung to the intake pipe that was meant for the air pump hose I discovered that the pipe on the pump itself was not a standard size. Instead of 3/4" or 1" it was 7/8". The GoodRidge hose wouldn't fit on the 7/8" pipe no matter how hard I tried. So I gritted my teeth and fabricated a new part for the pump. After screwing up once I succeeded and it's actually pretty cool.
4. Vent filter: As you can see one hose has a small vent filter on it instead of being plumbed in to the rest of the intake. I have seen other designs where it is but since nobody I asked knew what it was I decided it best to keep it separate because that is how it is on the stock air box. It enters the stock box on the upper right corner where it is isolated with a small subsection of the air box, which contains a foam filter. The exit/entry point is on the side of the box where a plastic pipe is attached that wraps under the box to where it sits open.
5. BOV: Upgrading the blow off valve (BOV) is a popular upgrade but in comparisons the stock BOV on this car is of exceptional quality. It also offers the ability to plumb the released boost pressure back in to the intake track to help the keep turbos spooled. (Oh darn, I don't have the rice boy whistle sound between shifts.) The BOV can also suck air in to the engine under certain conditions so I believe it is important to filter the air regardless. I plumbed the BOV in to the primary turbo's intake pipe.
6. CRV: The charge release valve (CRV) is used in the sequential turbo system's pre-spool process and was plumbed in to the secondary turbo's intake pipe.
7. Primary turbo's ducting: This filter is a perfect cylinder so I calculated the area of the 2.5" pipe and determined the size of the shield I needed to allow that same area around the filter. So basically the filter "can" is big enough so as to not restrict flow around and in to the filter. At the bottom of the can is a rectangular opening that was again designed to maintain at least the same area of the pipe. The back of the can is riveted in to place and sealed with silicone. The filer back is pressed against the opening that I cut in to it for a tight seal. The front is attached by 4 screws so that I can easily remove it for filter removal and cleaning. The entire duct is held in place by 2 bolts that attach to the chassis on the left side.
8. Secondary turbo's ducting: The Kool Blue filter is not a perfect cylinder and is instead tapered with a second smaller filtration element at the top. The heat shield on this filter is flush against the widest part of the filter and because of the taper opens up towards the filter's top. I again calculated the area of this "ring" to make sure it's area was at least that of the 2.5" pipe. The heat shield is open on both ends and is held on a round shape with two folds at the bottom that lock together. Instead of fabricating an entire duct to attach to the intercooler duct I hacked the Racing Beat duct to pieces are shortened it. It is held in place by a aluminum bracket. I then connected the two with a fiberglass thing. I say thing because I didn't do a great job. I honestly didn't know how to create the custom shape out of fiberglass and have it turn out nice and smooth. Instead it is functional only. It is attached with screws. The filter is accessible by first removing the fiberglass duct and then the heat shield. All of the shielding for both filters will be painted with ceramic paint to help keep heat out eventually.

Conclusion: The results are awesome. The pipes remain cool, which proves that this is a cold air intake and the performance is surely enhanced. (Ok so I don't have proof.) It is a unique part in a different car, not just another bolt-on attached to a Honda Civic. Some people like to think their car's are customized but really they are just a number of different parts from different manufactures. It's not until you actually do something that can't be easily duplicated that you truly have a customized car.